The present disclosure relates to a spray gun and, more specifically, a spray gun with a safety switch and an on-off switch.
Such spray guns are customarily operated by a liquid medium under high pressure.
Work with spray guns is characterized by high physical stress for the operator as a result of the high holding and recoil forces, the limited view because of fog formation and the humid environment. In addition, a high risk potential is created by the rebounding of material but mainly by the high energy content of the liquid jet, normally a water jet. On the one hand, this requires a construction with a good ergonomic design and the highest safety standard and, on the other hand, that only correspondingly instructed personnel trained for the work with high-pressure water jets are permitted to work with spray guns.
The operation of the spray gun by mechanical or electromechanical operating elements is known.
In this case, an on-and-off switching takes place by a manual lever which is arranged in the handle part and which can be blocked in an inoperative position by a safety switch. For operating the manual lever, a prior releasing of the safety switch from its locking position is therefore required.
However, the function of the manual lever can be achieved only at relatively high constructive expenditures. These expenditures comprise many complicated parts which, on the one hand, require a fairly expensive production and, on the other hand, are relatively susceptible to disturbances. Fragments and residues of the material to be processed by the spray gun may enter into the area of the lever linkage and of the safety device and block the lever linkage and the safety device.
Mechanical lever systems generally require the application of an operating or holding force by the operator. In this case, the operator's hand must necessarily always remain in contact with the lever. During a fairly long switch-on period, this leads to fatigue or even to cramps in the switching hands. As a result, safety-critical situations may arise; for example, because of the fact that the switch-off cannot take place or can only take place in a delayed manner.
It is known from practice that, because of the strained working position, the operating personnel frequently fixes the lever devices by simple means, such as wooden wedges, wire or adhesive tape, against safety regulations, in order to reduce the holding force.
In the case of the construction known from German Patent Document DE 86 11 018 U1, the operation takes place by contactless electronic proximity sensors, for example, according to the inductive principle. The sensor converts a physical quantity to an electric signal and utilizes its change for generating a switching function. Here, the influencing element, which the operator utilizes for the switching, is of a passive nature in that no communication takes place between the operating element and the proximity sensor. This results in the disadvantage of this state of the art that the system can easily be disturbed or even unintentionally switched as a result of outside influences, such as magnetic or electric fields, vibrations or temperatures. Furthermore, safety regulations are easy to bypass by permanently mounting the operating element on the proximity sensor, for example, by adhesive tape or wire. A self-monitoring of the electronic circuit and a checking of the access authorization is not possible or not provided.
Depending on the type of construction, the guidance of the medium is also unsatisfactory in the two constructions. This means that performance-reducing turbulences and frictional losses occur as a result of hydraulic valves and T-shaped or angular connection elements which impair the efficiency of such spray guns.
The handling of these spray guns is also unsatisfactory. Particularly from an ergonomic point of view, their extended use may be detrimental to an operator's health, for example, as a result of muscular tenseness or the like.
The spray gun of the present disclosure has significant advantages in comparison to the state of the art. The contactless actuation of the spray gun without moving parts takes place by an active system which is distinguished by the fact that the actuating element, preferably a transponder, communicates with a reading station of an electronic evaluating device within the spray gun. As a result, it becomes possible to ensure the highest possible safety standard for the operator as well as for persons and objects in his environment.
The transponder is a microelectronic circuit with a transmitting and receiving antenna, a control logic and a fixedly stored safety code as well as an energy accumulator which provides the energy for the return of the safety code. The transponder receives energy packets pulsed at regular intervals from the reading unit of the spray gun and returns information. This takes place by way of antennas in the handle tube which are arranged in pairs in order to generate a concentric field without pole points so that a uniform defined switching interval is ensured.
The transponder has a unique identification number which, when it is entered into the antenna field, is sent to the reading unit by the transponder in order to enable the authorization. This reading unit checks the identification code and makes a decision concerning the enabling. Thus, it is ensured that only authorized persons can start the operation of a spray gun and outside influences cause no safety-relevant malfunctioning.
The transponder is arranged as a separate part, for example, in the user's finger range. Here, it may, for example, be a component of a glove, a finger ring or a finger covering. The switch-off takes place by moving the transponder out of the antenna field.
The protection against an unintentional actuating is ensured by a safety switch without movable parts, preferably a piezo key. When actuated, the latter enables the switch-on function for a certain time, specifically only when previously no transponder has been situated in the antenna field. As a result, a bypassing of the OFF-function by a permanent mounting of the transponder on the handle pipe, for example, by gluing, is prevented. The enabling time window can be adjusted by an external evaluating and programming unit and typically amounts to 1–3 seconds.
By way of the program of the evaluating device, the function of a circuit breaker is also assigned to the safety switch. In addition to moving the transponder out of the antenna field, this provides a second possibility of changing the system to a safe pressureless condition.
The reading and evaluating unit is conceived to be self-monitoring, so that, in the case of defects within the electronic unit, the system itself is automatically always changed to the safe, that is, non-energized condition. This is achieved by a second transponder which is fixedly installed on the printed circuit board together with a reference antenna. Before each enabling, by inactivating the testing transponder, the electronic unit internally examines whether an off-command is taking place. Only when this is properly implemented, will the external switching function be enabled. The signal exchange takes place dynamically by way of radio communications; that is, with an alternating switching of the antennas between the transmitting and receiving mode, so that a defective final stage of the electronic unit immediately results in a switch-off.
Furthermore, the present spray gun offers the possibility of reading out, by way of a connected evaluating and programming unit, operating data which are detected and stored by the electronic evaluating unit of the spray gun, such as switch-on periods with the date and the time, the summed-up operating duration or the like. These data can be used for controlling the working times, as a basis of calculation and planning as well as in the sense of a preventive servicing and maintenance of the pressure-guiding system. This also results in a significant advantage with respect to the state of the art, where this has so far not been possible.
In addition, by way of an external programming, the spray gun offers the possibility of a remote control without accessory parts. For this purpose, an external command is assigned to a certain combination of signals of the safety key and of the transponder. Thus, for example, by actuating the safety key three times within a permissible, also programmable time window, a high-pressure aggregate can be switched on for supplying the spray gun. In this case, the actuation may be indicated by acoustic signals.
The spray gun is conceived to be essentially independent of constructional requirements caused by the function. Thus, for example, the media flow can be optimized; that is, it is to be designed such that turbulences and/or hydraulic resistance are very slight so that the friction losses on the whole are minimized. The efficiency of the spray gun is optimized to a considerable extent.
The new spray gun also offers unlimited possibilities with respect to an ergonomic design freedom.
As a result of the absence of, in particular, movable components, the spray gun can now be produced at a significantly lower price and is not susceptible to interfering influences, such as becoming dirty. Also, parts which are subject to wear are eliminated, so that the service life of the spray gun is increased, in fact, is virtually unlimited, at least with respect to the wear caused by the operation.
The nozzle tube and the feed line are connected with one another in the area of the handle part by an uninterrupted connection tube. They can be bent in one piece from a tube which has a continuously smooth wall on the interior side.
The site of the switching is not defined in a punctiform manner but as a surface. Therefore, the user can grip the spray gun at any point of the switch surface and in the process switch it on and off or leave it in the switched-on condition.
When the nozzle tube is very short, it is possible that the operator's hand may reach the danger range of the water jet. In order to avoid this, according to the disclosure, an additional switch surface can be provided on the handle part, and the operator can be equipped with a second actuating element. Before an enabling, the electronic evaluating unit of the spray gun will then examine whether both hands are within the range of the switch surfaces and thus outside the danger range of the water jet.
Naturally, the spray gun is not limited to a use as a spray gun for liquid media but is definitely also suitable for a use as a compressed-air spray gun.
These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings.